Renault boss Eric Boullier believes it will be very difficult for the FIA to please all parties over the current exhaust-blown diffuser row in Formula One.

On Friday it emerged that the engine manufacturers had been granted some concessions over the ban on off-throttle blown diffusers for reliability reasons. In the team principals' press conference McLaren and Red Bull rowed over who the changes would benefit most, with both claiming the other would retain an advantage.

The problem is that Renault engines cold-blow the diffuser (leaving the throttles open but not injecting fuel) while Mercedes hot-blow (allowing fuel to flow through the combustion chamber but retarding the ignition so it combusts in the exhaust). Boullier, whose cars use the same Renault engines as Red Bull, believes the FIA technical delegate Charlie Whiting will struggle to find an equalising formula that restricts off-throttle blowing equally among all the engines while maintaining reliability.

"I reckon that if Charlie is trying to please every engine manufacturer it would be very difficult to create a level playing field," he told reporters.

He said he had not learnt anything from Friday's practice sessions because of the wet weather but could not "see how we could make a level playing field."

He also revealed that a member of the Renault engine team had been in contact with the FIA all weekend. "Renault since yesterday [Thursday] is living in the office of the [FIA]."

Exhaust blowing has been central to the design of the Renault since its launch, with the car featuring front-exiting exhausts to energise the flow of air along the length of the floor. However, Boullier confirmed that Renault had run a standard exhaust configuration at a straight-line test recently and did not rule out the new layout making it to a practice session this season.

"We have to we have to evaluate all scenarios on this side as well," he said. "Our concept at the front was to maximise the blowing floor and now we have to move ahead and think differently, because anyway next year it won't be allowed. We still have our concept, we still actually have a lot of gains coming in the coming weeks. But we won't spend too much to develop this one if it's forbidden next year."

He said much would depend on the final decision by the FIA on how to restrict off-throttle blowing this season, but admitted the other system was not yet ready.

"To be honest it's too early," he said. "We have built it up and we have tested it at the aero tests, but we still need to wait to see the loss from this blowing to see if we want to bring it to one of the free practices."